How can I use Oracle views with Geoserver and WFS-T?

Question

What goes on when Geoserver handles updates to my table using WFS-T?

I have a table

AREA (
ID NUMBER(10) NOT NULL PRIMARY KEY,
SOME_OTHER_ID NUMBER(10) NOT NULL FOREIGN KEY REFERENCES FOO(ID),
GEOMETRY MDSYS.SDO_GEOMETRY NOT NULL
);

and a sequence SEQ_AREA for the primary key values.

When I publish this table as a Geoserver layer, it seems that it automatically detects that ID is the primary key and does not show it in the layer's properties.

When a new row is inserted, Geoserver does not use the index - how does it determine the next value? Does it do SELECT MAX(id) FROM AREA or something like that? Could I make it use the sequence?

And - if I create a view and a layer from that - the view does not have primary key as such - how can I make Geoserver understand it so that it is updatable? When I create a view such as:

CREATE VIEW TESTVIEW AS
  SELECT a.ID, foo.somefield, a.some_other_id, a.GEOMETRY 
  FROM FOO foo, AREA a
  WHERE foo.ID = a.SOME_OTHER_ID;  

insert into USER_SDO_GEOM_METADATA (table_name, column_name, diminfo, srid)
values ('TESTVIEW ',
'GEOMETRY',
SDO_DIM_ARRAY
(
  SDO_DIM_ELEMENT('X',50199, 761274,0.5),
  SDO_DIM_ELEMENT('Y',6582464, 7799839,0.5)
),
3047); 

The layer ends up being viewable OK, but cannot be updated / inserted. When updates are attempted through wfs-t I get:

2013-02-26 19:00:33,636 ERROR [org.geoserver.ows] - org.geoserver.wfs.WFSTransactionException: {http://www.opengeospatial.net/cite}TESTVIEW is read-only

Answer 1

I solved this by adding a database trigger which modifies attempts to update the view's data (which is not possible since it is read-only) into updates to the source data. Like so:

CREATE OR REPLACE TRIGGER AREA_INSERT 
INSTEAD OF INSERT ON TESTVIEW
REFERENCING NEW AS n 
     FOR EACH ROW
BEGIN
  insert into area (id, some_other_id, geometry) values (:n.ID, :n.some_other_id, :n.geometry); 
END;
/

...and a similar trigger for updates.

I also seem to have disabled primary key constraint for this view

alter view TESTVIEW add constraint TESTVIEW_PK primary key (ID) disable;

but can't remember why this was important.